What's your choice for cloud storage? (I got a mbpro with 128gb SSD but don't like external drive)

Backups or just extended storage space?

Both I guess but mainly extended storage

I like to be redundant with backing things up so I use quite a few different options. ArqBackup is really good and easy for connecting to whatever cloud backup you choose (Highly recommend using this). I also like using BackBlaze with their full Mac auto Backup option along with setting up different buckets for certain things that aren't covered by their full auto backup and anything else that pops up. Beyond that you could also do AWS S3 and or something like Google Glacier depending on what exactly you're looking for. If you're looking for something minimal and physical (and if you can work with a non USB Type-C) you could do something like the SanDisk Ultra Fit 128GB USB 3.0 Flash Drive…, which is super small and will double your local storage. You could also use a SATA to USB converter cable with a normal SSD if that interested you.